With Bacteria, ‘Physical Forces Can Change Biological Fate’

It’s not unusual for biologists to spend years intensively studying a single species or phenomenon. Professor Nicolas Biais (GC/Brooklyn; Biology, Physics/Biology) spent more than three years on research that recently appeared in Scientific Reports, an online journal published by Nature.

The study found that single-cell bacteria with identical features behaved differently depending on their location in a microcolony. Bacteria near the surface used microscopic appendages called pili to move around. In contrast, bacteria in the microcolony’s core were more static, bonded to each other by their pili. The different behaviors also led to a differentiation in gene expression.

Not only did these identical cells exhibit different behavior, but the active surface cells used their mobility to form bridges between small microcolonies. Once those smaller microcolonies were connected, the larger colony rearranged into a new shape, again thanks to the movement of those surface bacteria.

Bacterial cells in a microcolony are covered in protein filaments, or pili, which bind the cells together. Image courtesy of the Biais lab.

Biais said the research “is trying to establish the idea that mechanics play a role in the bacterial world, which is something that not many people have realized.” The next phase will explore “how you go from those potential forces to the gene expression. What’s triggering it? … What is it, in the bacterial cell, that senses the changes, that leads to the gene expression?”

Biais’ research has implications for human health because he’s using the bacteria that cause gonorrhea. Microcolonies are also the first stage in the development of biofilms, which are bacterial communities that stick to a surface.

Biais conducted the live bacteria work in his lab in collaboration with other CUNY researchers, including Graduate Center Ph.D. student Kelly Eckenrode (Biology). But computational modeling for the study was done in Germany. Because it takes so long to master the specialized equipment and techniques needed for this type of interdisciplinary research, Biais said it’s not unusual for scientists to assemble a team of expert collaborators across the world and share research both online and in person. Besides, he said, “Science is a human endeavor. Interacting with other people, that’s part of the joy and the drive.”